Despite advances in vaccine development and antimicrobial therapies, infectious diseases remain widespread. Nationwide, at least 45 million people ages 12 and older, or one out of five adolescents and adults, have had genital Herpes infection. The prevalence of herpes simplex virus-2 (HSV-2) is increasing worldwide and there is now evidence linking it to HIV transmission. HIV has infected 40 million people to date and causes 2-3 million deaths each year (Joint United Nations Programme on HIV/AIDS, 2006 Report on the Global AIDS Epidemic, Ch. 2, 2006). Nine million new cases of tuberculosis were reported in 2005, with 1.6 million deaths in that year alone (Young et al., Clin Invest. 118(4):1255-1265, 2008). Malaria causes disease in hundreds of millions and kills 1-3 million each year (Snow et al., Nature 434 (7030):214-7, 2005). Efforts to limit the spread of these and other pathogens and control their devastating effects on human populations require effective vaccines. There remains a need for improved vaccines, and for systems to develop them.
The efficacy of many current vaccines lies in their ability to elicit robust antibody responses. However, T cell mediated immunity is important for protection from many types of infections, including those for which no effective vaccine is available. CD4+ T cells orchestrate humoral and cell mediated immune responses in vivo. CD8+ T cells are critical for the control of intracellular pathogens. Identifying antigens that elicit T cell mediated responses has been more technically laborious than characterizing humoral antigens.